General Electric Company

Harry M Laska

Nelson Grimm

Charles D Greskovich

Curtis E Scott

William J Ward, Iii

Mary Sue Kaliszewski

George L Gaines, Jr

Timothy J Gallivan

Patricia A Piacente

Peter C Smith

A high transmittance polycrystalline alumina arc tube for a metal halide discharge lamp is formed by treating an alumina arc tube material having a few percent of closed porosity in a two step process, which provides a high-transmittance arc tube. An initially porous arc tube is formed by extruding or die pressing individual components of the tube from a mixture which includes powdered alumina, assembling the components into an arc tube body, and then partially sintering the components to seal them together. The two step process includes hot isostatic pressing of the partially sintered arc tube and then chemically polishing the surface of the tube. The first, pressing step involves heating the alumina arc tube in an inert atmosphere, such as argon, at a temperature of 1600 to 1900&deg; C. and a pressure of about 700 to 2100 kg/sq.cm. for from about one to three hours. This reduces porosity in the crystalline structure. In the second step, the surface of the tube is immersed in a flux comprising a molten alkali metal borate at moderately elevated temperatures, or coated with a flux material which is heated to form the flux, to remove surface imperfections. The finished arc tube has transmittance values which approach those of single crystal sapphire arc tubes.

High transmittance alumina for ceramic metal halide lamps

A nuclear fuel material green body of density from about 30 to 70% of theoretical density having tensile strenght and plasticity adequate to maintain the integrity of the body during processing leading to ultimate sintered condition is produced by adding an amine carbonate or carbamate or mixture thereof to a particulate mass of the nuclear fuel material under conditions resulting in reaction with the amine compound to form a water-soluble compound effective as a binder for the particulate material.

Method of producing fugitive binder-containing nuclear fuel material

Increased optical transmission is provided for a body of light transmissive polycrystalline alumina having relatively uniform size equiaxed grains of alumina and which is essentially free of porosity and secondary phase material. A tube of the improved optical material can be used as the light transmissive envelope for high intensity discharge lamps especially sodium and other metal vapor lamps exhibiting increased light output as a result of said improved optical transmission. A method of producing the improved optical material is also disclosed.

Method of producing a tubular body of polycrystalline alumina

Polycrystalline alumina material

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Euclid, OH, United States of America

Harry M Laska